Single wafer type cleaning method and apparatus

ABSTRACT

A single wafer type wet-cleaning technique for wet-cleaning wafers, individually, which are not stored in a cassette, at the front and back faces thereof simultaneously, in a sealed cleaning housing, whereby a plurality of chemical fluids are vertically and sequentially supplied from a number of upper side supply nozzles  25  and lower side supply nozzles  26  to the front and back faces of each wafer W to clean the same, and purified water is always caused to flow out of the lower side supply nozzles  26, 26 , . . . , which do not supply chemical fluids, of the lower side supply nozzles, thereby preventing the occurrence of cross contamination of various chemical fluids between cleaning treatments.

This application is a Divisional of prior application Ser. No.09/948,952 filed Sep. 10, 2001.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a single wafer type substrate cleaning methodand a single wafer type substrate cleaning apparatus, more particularlyto a single wafer type wet-cleaning technique or system for applying acleaning treatment to substrates such as semiconductor wafers one by oneduring the fabrication process of semiconductors and devices such aselectronic parts and the like.

2. Prior Art

A so-called batch type wet cleaning system has been the principal methodof cleaning substrates such as semiconductor wafers (hereinafterreferred to simply as “Wafers”), whereby waters stored in a carriercassette are immersed in sequence in wet bench type cleaning bathsarranged in series, or wafers are directly immersed in the baths througha transfer unit without being stored in the carrier cassette. However,semiconductor devices have reached the sub micron age, in that they arenow micro-fabricated and highly integrated, such that the face of wafershas recently required a very high degree of cleaning density, and waferswhich are not stored in a cassette have to be wet-cleaned individuallyin a sealed cleaning housing. To this end, a so-called single wafer typewet cleaning system intended to meet the requirement of a highercleaning density has been developed and proposed. The present applicanthas improved this single wafer type wet cleaning method, and filedJapanese Patent Application No. 2000-370718 for such improvement. Thesaid invention relates to a method for effectively preventing oxidationon the front faces of wafers while optimizing the benefits of the singlewafer type substrate wet-cleaning system for cleaning wafers,individually, which are not stored in a cassette, in a sealed cleaningchamber.

Under the single wafer type wet cleaning system, wafers can be cleanedwith the use of a simple and compact cleaning apparatus in a relativelyclean atmosphere where particles and the like do not settle or remain onthe face of the wafer. This system is therefore practical to use forsmall scale production.

Generally, under the single wafer type wet cleaning system, the frontface, i.e., the upper side surface of the wafer, is cleaned by theapplication of various chemical fluids in a predetermined order, andrecently, a technique whereby both the front and back faces of waferscan be simultaneously cleaned has also been developed. Basically, theback face i.e., the lower side surface of the wafer, is cleaned by theinjection and supply of chemical fluids from the lower side surface tothe upper side surface of the wafer, giving rise to the probability ofcross contamination of the wafer by the different chemical fluidsbetween cleaning treatments. The present invention therefore seeks toaddress this problem of cross contamination.

SUMMARY OF THE INVENTION

The object of the invention is to provide a single wafer type wetcleaning technique capable of simultaneously wet cleaning the front andback faces of wafers, individually, which are not stored in a cassette,in a sealed cleaning chamber.

To achieve this object, the proposed invention comprises a single wafertype cleaning method for wet-cleaning wafers, individually, which arenot stored in a cassette, in a sealed cleaning housing, whereby thefront and back faces of each wafer, which is rotatably supported in thecleaning housing, are vertically and sequentially supplied with variouschemical fluids from upper and lower side supply nozzles and purifiedwater is always made to flow out of at least one of the lower sidesupply nozzles which does not supply any chemical fluid.

In the preferred embodiment, the single wafer type substrate cleaningmethod further comprises a rinsing treatment of each wafer by supplyingpurified water from the upper and lower side supply nozzles which supplychemical fluids between cleaning treatments and a cleaning treatment bysupplying various other chemical fluids in another series of cleaningtreatments, and by causing purified water to continuously flow out of atleast one of the lower side supply nozzles upon completion of therinsing treatment. In this case, it is preferable that the flow of thepurified water from the lower side supply nozzle shall be of minimumvelocity to prevent the counter flow of chemical fluids other than thechemical fluids supplied from the lower side supply nozzles.

Further, the single wafer type substrate wet-cleaning apparatus of theinvention is suitable for carrying out the foregoing cleaning method andcomprises (1) wafer rotary means for supporting and rotating a singlewafer in the cleaning housing in the horizontal position, (2) a cleaningchamber provided at the outer peripheral portion of the wafer rotarymeans for forming a cleaning treatment space for cleaning the waferwhich is rotatably supported by the wafer rotary means, and (3) chemicalfluid supply means for supplying chemical fluids to the front and backfaces of the wafer which is rotatably supported by the wafer rotarymeans, wherein the chemical fluid supply means is provided in thecleaning housing and consists of upper side supply nozzles for supplyingchemical fluids to the front face of the wafer from the upper side ofthe cleaning housing and lower side supply nozzles for supplying thechemical fluids to the back face of the wafer from the lower sidethereof, and wherein the upper and lower side supply nozzles verticallyand sequentially supply a plurality of chemical fluids to the front andback faces of the wafer which is rotatably supported by the wafer rotarymeans, thereby cleaning the wafer, and purified water is always made toflow out of the lower side supply nozzles which do not supply chemicalfluids, of the lower side supply nozzles, in a series of cleaning steps.

In the preferred embodiment, the upper and lower side supply nozzles arecomposed of injection nozzles for injecting and supplying the chemicalfluids to the front and back faces of each wafer which is rotatablysupported by the wafer rotary means, and the number of supply nozzlesemployed depends on the kind of chemical fluids to be supplied. Further,the lower side supply nozzles are directed upward and located on theupper end portion of the rotatable rotary shaft of the wafer rotarymeans, and they can communicate with either the chemical fluid supplysource or the purified water supply source.

Notably, it is preferable that a gap is established between the innerperiphery of the rotary shaft of the wafer rotary means and the outerperiphery of the pipe to serve as a supply port of inert gas.

Under the single wafer type cleaning system of the invention, waferswhich are not stored in a cassette, are individually cleaned in thesealed cleaning housing, by vertically and sequentially supplyingvarious chemical fluids from the upper-and lower supply nozzles to thefront and back faces of each wafer which is rotatably supported by thewafer rotary section.

In this case, purified water is always caused to flow out of the lowerside supply nozzles which do not supply chemical fluids, of the lowerside supply nozzles, in order that cross contamination of such chemicalfluids can be prevented between cleaning treatments of the wafers.

In detail, when chemical fluids are supplied to the back face of eachwafer from the lower side to the upper side, some of the chemical fluidsare prone to remain in the lower side supply nozzles as the lower sidesupply nozzles are constructed in such manner as to be opened upward.Accordingly, when the cleaning treatment is effected by another chemicalfluid upon completion of the cleaning treatment by a particular chemicalfluid, the chemical fluid remaining in the lower side supply nozzles inthe preceding cleaning treatment(s) mixes with other chemical fluids inthe succeeding cleaning treatments, or, chemical fluids supplied betweencleaning treatments enter the lower side supply nozzle 26 which is onstandby so that such chemical fluids mix with a different kind ofchemical fluid remaining in the standby supply nozzle 26, giving rise toa high probability of cross contamination of the chemical fluids betweencleaning treatments.

In consideration of the foregoing problem, according to the invention,purified water is always made to flow out of the lower side supplynozzles which do not supply chemical fluids, of the lower side supplynozzles, so that the anticipated occurrence of cross contamination ofvarious chemical fluids between cleaning treatments can be avoided.

Under the single wafer type substrate cleaning system of the invention,a plurality of chemical fluids are sequentially supplied from the upperand lower supply nozzles to the front and back faces of each wafer whichis rotatably supported by the wafer rotary means such that each wafer,which is not stored in a cassette, is wet-cleaned in the sealed cleaninghousing, wherein purified water is always made to flow out of the lowerside supply nozzles which do not supply chemical fluids, of the lowerside supply nozzles, so that cross contamination of various chemicalfluids between cleaning treatments can be prevented.

In other words, when the supply of chemical fluids to the back face ofeach wafer is effected from the lower side to the upper side, thechemical fluids which are prone to remain in the lower side supplynozzles because of the upward manner in which they are constructed mixwith other chemical fluids supplied between cleaning treatments uponcompletion of each cleaning treatment by one chemical fluid, as wouldlead to cross contamination of such chemical fluids. According to theinvention, therefore, it is possible to effectively prevent theoccurrence of cross contamination of various chemical fluids betweencleaning treatments by causing purified water to flow out of the lowerside supply nozzles which do not supply chemical fluids, of the lowerside supply nozzles.

BRIEF DESCRITPTION OF THE DRAWINGS

FIG. 1 is a front sectional view showing the internal construction of asingle wafer type substrate cleaning apparatus according to thepreferred embodiment of the invention;

FIG. 2 is an enlarged front sectional view showing the locationalrelationship between the wafer rotary section, the cleaning housing, andthe chemical fluid supply section of the single wafer type substratecleaning apparatus;

FIG. 3 is an enlarged front sectional view showing the construction ofthe wafer rotary section and the lower side injection nozzles of thechemical fluid supply section;

FIG. 4 is an enlarged plan view showing the construction of the waferrotary section and the lower side injection nozzles of the chemicalfluid supply section;

FIG. 5 is an enlarged front view showing the lower side injectionnozzles of the chemical fluid supply section and the peripheralconstruction thereof.

PREFERRED EMBODIMENT OF THE INVENTION

The preferred embodiment of the invention is described with reference tothe attached drawings.

A single wafer type substrate wet-cleaning apparatus is illustrated inFIG. 1, wherein each wafer W, which is not stored in a cassette, isindividually wet-cleaned in a sealed cleaning housing 1, and thesealable cleaning housing 1 comprises a wafer rotary section (waferrotary means) 2 for rotatably supporting one wafer W in the horizontalposition, a cleaning chamber 3 which is relatively vertically movable, achemical fluid supply section (chemical fluid supply means) 4 forsupplying chemical fluids to the front and back faces of the wafer, aninert gas supply section (inert gas supply means) 5 for supplying aninert gas for preventing oxidation, and a controller 6 for controllingthese driving sections while interlocking mutually therewith as majorcomponents.

The cleaning housing 1 is sealable at the upper portion for the cleaningtreatment and serves as a location for installing various unit drivingsections at the lower portion disposed in the upper space. A closablewafer taking in-out port, not shown in detail, through which the wafer Wis taken in or taken out in the upper space of the cleaning housing 1,is structured in such a way to secure airtightness and watertightnesswhen it is closed.

The wafer rotary section 2 horizontally rotates a single wafer W whileit supports the single wafer W in the horizontal position when the spincleaning and spin drying treatments are applied thereto, and comprises arotary shaft 10, a wafer supporting section 11 which is attached to andsupported by the upper end portion of the rotary shaft 10 in thehorizontal position, and a driving motor 12 for rotatably driving therotary shaft 10.

The wafer supporting section 11 and the rotary shaft 10 are rotatablydisposed at the center of the cleaning housing 1 via a bearingsupporting cylinder 13 in a perpendicular position, and the wafer W canbe supported by the wafer supporting section 11 in the horizontalposition.

In particular, the wafer supporting section 11 is composed of a discbody, as shown in FIGS. 3 and 4, and has a plurality of columnarsupporters, 14, 14, . . . (four pieces of which are shown in FIG. 4) forplacing and supporting the peripheral portion of the wafer W on theouter peripheral portion of the upper face thereof.

These supporters 14, 14, . . . are arranged circumferentially on thewafer supporting section 11 with the same intervals as illustrated, andthe inner peripheral portion of the upper ends thereof support theperipheral portion of each wafer W to form supporting recesses 14 a, 14a, . . . . The supporting recesses 14 a, 14 a, of these supporters, 14,14, . . . are designed to have the same height, so that the peripheralportion of the wafer W is supported when it is placed thereon in thehorizontal position.

Further, the supporting face of each supporting recess 14 a has aconfiguration corresponding to the contour of the peripheral portion ofthe wafer W in cross section, and the peripheral edge corner section ofeach supporting recess 14 a can contact and support the squareperipheral corner of the wafer W in cross section in a point contactstate or line contact state.

The rotary shaft 10 is rotatably supported by a bearing 40 via thebearing supporting cylinder 13 in the standing position, and the lowerend portion of the rotary shaft 10 is connected to the driving motor 12via a belt entrained therebetween so as to be rotatably driven by thedriving motor 12 so that the wafer supporting section 11 is rotated at agiven speed of rotation. The speed of rotation of the rotary shaft 10 isset at low speed, e.g., 40-50 r.p.m. when the spin cleaning treatment iseffected while it is set at high speed of approximately 3000 r.p.m. whenthe spin drying treatment is effected.

Further, the rotary shaft 10 is composed of a hollow cylindrical body asillustrated, and a pipe 30 for the lower side supply nozzles 26 of thechemical fluid supply section 4, described hereinbelow, which isdisposed in the hollow section of the rotary shaft 10.

The cleaning chamber 3 is the section where the cleaning treatment isapplied to the wafer W, and the inner diameter dimensions thereof aredetermined in connection with the wafer supporting section 11 of thewafer rotary section 2, described hereinbelow, and has a cleaningtreatment space for cleaning the wafer W, which is rotatably supportedby the wafer rotary section 2, at the outer periphery of the waferrotary section 2.

In detail, the cleaning chamber 3 has plural stages of annular treatmentbaths 15 to 18 which are arranged vertically at the inner peripherythereof as shown in FIGS. 1 and 2, and it is constructed to move up anddown vertically relative to the wafer rotary section 2.

In the illustrated preferred embodiment; four stages of annulartreatment baths 15 to 18 are arranged vertically and concentrically withthe wafer W so as to surround the wafer W which is supported by thewafer supporting section 11 of the wafer rotary section 2.

The peripheral inner edges of the annular treatment baths 15 to 18 arearranged in the manner that annular gaps defined between these edges areset to have small intervals to such extent as would prevent the chemicalfluids and the like from being leaked downward and at the same time donot contact the outer diameter edge of the wafer supporting section 11of the wafer rotary section 2.

The cleaning chamber 3 is supported to be movable up and down, i.e.vertically via an elevating guide (not shown), and has an elevatingmechanism 20 capable of elevating relative to the wafer supportingsection 11 of the wafer rotary section 2 by a given stroke.

The elevating mechanism 20 comprises a feed screw mechanism, (notshown), which moves a supporting frame 21 for supporting the cleaningchamber 3 up and down, and a driving motor 22 for rotatably driving thefeed screw mechanism.

Depending on the cleaning treatment step, the cleaning chamber 3 movesup and down vertically by a given stroke via the feed screw mechanism asthe driving motor 22 is driven while interlocking with the operation ofthe wafer rotary section 2, described hereinbelow, so that any one ofthe annular treatment baths 15 to 18 for effecting the cleaningtreatment step may be selected from a position of height relative to thewafer W which is supported by the wafer supporting section 11 of thewafer rotary section 2.

Drain sections, which communicate with the outside of the apparatus, arerespectively provided in the four annular treatment baths 15 to 18 (notillustrated in detail). These drain sections discharge or collect forrecycling the chemical fluids or the inert gas inside the annulartreatment baths 15 to 18, in which they are structured to be opened onlywhen the cleaning treatment is effected and to be closed when thecleaning treatment is effected in other treatment baths.

The chemical fluid supply section 4 supplies the chemical fluids to thefront and back faces of the wafer W which is rotatably supported by thewafer rotary section 2, and it has upper side supply nozzles 25 forsupplying the chemical fluid to the front face of the wafer W from theupper side thereof and lower side supply nozzles 26 for supplying thechemical fluid to the back face of the Wafer W from the lower sidethereof.

In detail, these upper side supply nozzles 25 and lower side supplynozzles 26 comprise the injection nozzles for injecting and supplyingthe chemical fluids to the front and back faces of the wafer W, whereinthe number of the supply nozzles to be employed depends on the kind ofchemical fluids to be supplied. The upper side supply nozzles 25 andlower side supply nozzles 26 can communicate with the chemical fluidsupply source 27 provided outside the cleaning housing 1.

In the illustrated embodiment, the upper side injection nozzles 25 arelocated in the injection nozzle section 25A which integrally consists ofa plurality of nozzle sections, and the injection nozzle section 25A isconstructed in such a manner that it may be turned horizontally in adownward direction at the upper portion of the cleaning housing 1, andit is drivably connected to a driving motor capable of being swung, (notshown).

The injection nozzles to be utilized depends on the kind of chemicalfluids to be supplied. In particular, these four upper side injectionnozzles 25, 25, . . . which are provided in the injection nozzle section25A, (not shown), are intended to serve as supply ports for APM fluid,purified water, and DHF fluid, described hereinbelow.

The upper side injection nozzles 25 of the injection nozzle section 25Aare constructed in such a way as to inject and supply given chemicalfluids to the front face Wa of the wafer W which is rotatably supportedby the wafer supporting section 11 of the wafer rotary section 2 in thehorizontal position while it is turned horizontally from the outerregion toward the center thereof or when it stands still after beingturned horizontally.

The lower side injection nozzle 26 is provided on the upper end portionof the rotatable rotary shaft 10 of the wafer rotary section 2, and itis firmly provided relative to the back face of the wafer W in an upwarddirection. In the illustrated preferred embodiment, two sets of lowerside injection nozzles 26, 26, . . . are disposed corresponding to theupper side injection nozzles 25, 25, . . . respectively for APM fluid,purified water and DHF fluid. In particular, a total of 6 lower sideinjection nozzles are provided as shown in FIG. 5.

These lower side injection nozzles 26, 26, . . . can communicate withthe chemical fluid supply source 27 via the pipe 30 disposed inside therotary shaft 10 as shown in FIGS. 3 to 5.

In detail, the pipe 30 vertically penetrates the hollow section of therotary shaft 10 composed of a hollow cylindrical body and is firmlydisposed on the rotary shaft 10 by a supporting structure, (not shown),while it does not contact the rotary shaft 10.

A discoid chemical fluid supply section 31 is affixed to the upper endportion of the pipe 30 and six lower side supply nozzles 26, 26, . . .are disposed circumferentially on the upper face of the chemical fluidsupply section 31 at the same intervals, wherein each lower sideinjection nozzle 26 is in an upward slanting position relative to thecenter of the back face of the wafer W which is rotatably supported bythe wafer rotary section 2.

These lower side supply nozzles 26, 26, . . . communicate with thechemical fluid supply passages 30 a, 30 a, . . . which are locatedwithin the pipe 30. The chemical fluid supply passages 30 a, 30 a, . . .can selectively communicate with the supply source of the chemicalfluids (APM fluid and DHF fluid) of the chemical fluid supply source 27or the supply source of purified water via a directional control valve32 at the lower end portion of the pipe 30. The chemical fluid supplypassages 30 a, 30 a, . . . also communicate with the upper sideinjection nozzles 25, 25, . . . .

The chemical fluid supply source 27 is the supply source for supplyingchemical fluids to the upper side injection nozzles 25, 25, . . . , andlower side injection nozzles 26, 26, . . . , and in the illustratedembodiment, has two chemical fluid systems, from which either aconstruction for cleaning the wafer W by APM (NH₄OH+H₂O₂+H₂O) fluid or aconstruction for cleaning the wafer W by DHF (HF+H₂O) fluid may beselected, while the annular treatment baths 15 to 18 in the cleaningchamber 3 correspond to these two chemical fluid supply systems, suchthat, the lowermost stage treatment bath 15 is used for the cleaningstep by APM fluid, the third upper stage treatment bath 16 is used forthe cleaning step by DHF fluid, while the second upper stage treatmentbath 17 is used for the rinsing step by purified water, and theuppermost stage treatment bath 18 is used for the spin drying step.

Further, the chemical fluid supply source 27 is constructed to selectand effect the cleaning steps using any of the following recipes ofchemical fluids: i) APM+DHF+(O₃+DIW)+DRY, ii) APM+DHF+DRY, iii) APM+DRY,DHF+DRY or the like with the cooperation of an inert gas supply source.37, described hereinbelow.

As described later, the upper side injection nozzles 25, 25, . . . andlower side injection nozzles 26, 26, . . . vertically and sequentiallysupply a plurality of chemical fluids to the front and back faces ofeach wafer W, which is rotatably supported by the wafer rotary section2, in accordance with the recipe which was selected from any of theabovementioned combinations i) to iii), thereby cleaning the wafer W,and they are driven and controlled to ensure that purified water isalways made to flow out of the lower side supply nozzle 26 which doesnot supply chemical fluids in the series of cleaning steps

The inert gas supply section 5 supplies an inert gas for preventingoxidation to the front and back faces of each wafer W which is rotatablysupported by the wafer rotary section 2 and is composed of an upper sidesupply section 35 for supplying an inert gas to the front face of eachwafer W and a lower side supply section 36 for supplying inert gas tothe back face of each wafer W as major components, wherein the upperside supply section 35 and the lower side supply section 36 cancommunicate with the inert gas supply source 37 provided outside thecleaning housing 1. In the illustrated preferred embodiment, the inertgas is a nitrogen gas (hereinafter, the “N₂ gas”).

The upper side supply section 35 is provided at the upper portion of thecleaning housing 1 and comprises a circular cover body for forming adrying sealed space at the periphery of the front face of each wafer Wwhich is rotatably supported by the wafer rotary section 2 whilecooperating with the cleaning chamber 3.

In detail, the outer diameter edge of the upper side supply section 35is designed to closely engage with the inner diameter edge of thecleaning chamber 3, i.e., the outer diameter edge of the uppermost stagetreatment bath 18, so that the requisite minimum drying sealed space isformed at the periphery of the front face of each wafer W which isrotatably supported by the wafer rotary section 2. The upper side supplysection 35 communicates with the inert gas supply source 37 via a pipe38.

The upper side supply section 35 is vertically movable between the useposition (not shown) cooperating with the cleaning chamber 3 and the usestandby position, i.e., the position of height shown in FIG. 1 whichdoes not interfere with the chemical fluid supply section 4, and isdrivably connected to an elevating means, not shown.

The lower side supply section 36 is provided on the upper end portion ofthe rotatable rotary shaft 10 of the wafer rotary section 2 in the samemanner as the lower side injection nozzle 26 is provided in the chemicalfluid supply section 4.

In detail, as shown in FIG. 5, a gap 39 defined between the hollow innerperipheral portion of the rotary shaft 10 of the wafer rotary section 2at its upper end and the outer peripheral portion of the pipe 30, i.e.,the chemical fluid supply section 31, serves as the supply port of thelower side supply section 36.

As shown in FIG. 5, the supply port 39 a of the lower side supplysection 36 opens to access the entire periphery of the cleaningapparatus in a horizontal radial direction in the interval between thelower face of the chemical fluid supply section 31 and the upper face ofthe wafer supporting section 11, and communicates with an inert gassupply passage 30 b defined by penetrating the inner center of the pipe30 via communication sections 31 a, 31 a, . . . which are defined bypenetrating the chemical fluid supply section 31 in a horizontal radialdirection, wherein the inert gas supply passage 30 b can communicatewith the inert gas supply source 37 via a directional control valve 41at the lower end portion of the pipe 30.

The lower side supply section 36 serves to prevent various apparatusdriving sections from being corroded inside the lower portion of thecleaning housing 1, which ensues from the backflow of the chemical fluidinto the gap 39 defined between the hollow inner peripheral portion ofthe rotary shaft 10 and the outer peripheral portion of the pipe 30, andso the inert gas is always to be injected and supplied from the lowerside supply section 36.

The inert gas supply section 5 having such a construction operates asthe wafer W is cleaned or the chemical fluid inside the cleaning chamber3 is discharged and replaced by another chemical fluid.

The controller 6 controls the movements of the components of the singlewafer type substrate cleaning apparatus while interlocking with thesecomponents, thereby automatically effecting the following series of wettreatment steps:

(1) Prior to the application of the cleaning treatment, the wafer W istaken into the wafer supporting section 11 inside the cleaning chamber 3via the wafer taking in/out port of the cleaning housing 1, (not shown),and after the cleaning chamber 3 is sealed, the wafer W is placed in thecleaning treatment position inside the cleaning chamber 3 by the up anddown movement of the cleaning chamber 3. Thereafter, the foregoingvarious cleaning treatments are effected in a predetermined procedure.

(2) For example, if the cleaning treatment is in the foregoing ii)cleaning treatment step (APM+DHF+DRY), the wafer W on the wafersupporting section 11 is first positioned and disposed in the lowermoststage treatment bath 15 and while the cleaning chamber 3 moves up anddown the APM fluid is injected and supplied from the upper sideinjection nozzles 25, 25, . . . and lower side injection nozzles 26, 26,. . . while N₂ gas is injected and supplied from the lower side supplysection 36 of the inert gas supply section 5, and the spin cleaningtreatment is applied to the wafer W as the wafer rotary section 2rotates at low speed.

In this case, purified water is always made to flow out of the lowerside supply nozzle which does not supply chemical fluids, particularly,from the supply nozzles 26 other than those which supply APM fluid. Theflow of the purified water from the lower side injection nozzle 26 shallbe have a velocity lower than the flow of chemical fluids supplied andejected therefrom, in order to prevent the counter flow of chemicalfluids other than the chemical fluid supplied from the lower sideinjection nozzle 26. The outflow of the chemical fluid from the lowerside injection nozzle 26 shall be in such state where it runs and sagsas shown in FIG. 5.

(3) Subsequently, the wafer W is positioned and disposed in the secondupper stage treatment bath 17, and purified water is injected andsupplied from all of the upper side injection nozzles 25 and lower sideinjection nozzles 26 while N₂ gas is supplied and ejected to the wafer Wfrom the lower side supply section 36 of the inert gas supply section 5,so that the rinsing treatment is applied to the wafer W as the waferrotary section 2 rotates at low speed.

Upon completion of the rinsing treatment, the upper side injectionnozzles 25 and lower side injection nozzles 26 are shifted to an outflowoperation of purified water at the flow velocity set forth above toensure that purified water continuously flows out.

(4) Further, the wafer W is positioned and disposed in the third upperstage treatment bath 16, and the DHF fluid is supplied from the upperside injection nozzles 25 and lower side injection nozzles 26 while N₂gas is supplied and injected from the lower side supply section 36 ofthe inert gas supply section 5, and the spin cleaning treatment isapplied to the wafer W as the wafer rotary section 2 rotates at lowspeed.

In this case, the outflow operation of purified water is continuouslyeffected from the lower side injection nozzle 26 which does not supplychemical fluids, particularly from the injection nozzles 26 other thanthose which supply DHF fluid.

(5) Further, the wafer W is positioned and disposed in the second upperstage treatment bath 17, and purified water is supplied from all of theupper side injection nozzles 25 and lower side injection nozzles 26while N₂ gas is injected and supplied from the lower side supply section36 of the inert gas supply section 5, and the rinsing treatment isapplied to the wafer W as the wafer rotary section 2 rotates at lowspeed.

(6) Finally, the wafer W is positioned and disposed in the uppermoststage treatment bath 18, while N₂ gas is supplied and injected from theupper side supply section 35 and lower side supply section 36 of theinert gas supply section 5, and the spin drying treatment is applied tothe wafer W as the wafer rotary section 2 rotates at high speed.

In the drying step, the upper side supply section 35 of the inert gassupply section 5 is lowered to the use position while cooperating withthe cleaning chamber 3, so that it forms a drying sealed space A whilecooperating with the cleaning chamber 3, and thereafter N₂ gas issupplied to and fills the drying sealed space A.

Accordingly, when contents of the drying sealed space A are purged andreplaced by N₂ gas, or when occasion demands, air current is produced inthe passage extending from the inert gas supply section 5 to the drainsection inside the drying sealed space A owing to the forceful airdischarge from the drain section of the uppermost stage treatment bath18, the concentration of oxygen on the periphery of the entire frontface of the wafer W becomes substantially zero (0), and thereafter thespin drying treatment is applied to the wafer W.

(7) The wafer W is again taken out via the wafer taking in/out port ofthe cleansing housing 1 upon completion of the series of cleaningtreatments in the single wafer type substrate cleaning apparatus.

Under the single wafer type substrate cleaning apparatus having theforegoing construction, a plurality of chemical fluids is sequentiallysupplied vertically from the upper side injection nozzles 25 and lowerside injection nozzles 26 to the front and back faces of each wafer Wwhich is rotatably supported in the sealed cleansing housing 1 so as towet clean it. Particularly, purified water is made to flow out of thelower side supply nozzles 26, 26, . . . which do not supply chemicalfluids so that cross contamination of various chemical fluids whichoccurs between cleaning treatments can be prevented effectively.

In other words, the supply of the chemical fluids to the back face ofthe wafer W is normally effected from the lower side toward the upperside but since the lower side supply nozzles 26 are structurallyinstalled to open upwardly, the chemical fluids are prone to remain inthe lower side supply nozzles 26, 26, . . . . Accordingly, when thecleaning treatments are effected by other types of chemical fluids insuccession, the chemical fluids that remain in the lower side supplynozzles 26, 26, . . . inevitably mix with the other chemical fluidsbetween cleaning treatments or, chemical fluids supplied betweencleaning treatments enter the lower side supply nozzle 26 which is onstandby so that such chemical fluids mix with a different kind ofchemical fluid which remains in the standby supply nozzle 26, givingrise to the probability of cross contamination in succeeding cleaningtreatments.

To address the foregoing problems, the single wafer type substratecleaning apparatus of the proposed invention, will cause purified waterto always flow out of the lower side supply nozzles 26, 26, . . . whichdo not supply chemical fluids, so as to effectively prevent theoccurrence of cross contamination of various chemical fluids betweencleaning treatments.

Although the foregoing embodiment is the preferred embodiment of theinvention, the invention is not limited to the foregoing embodiment butcan be redesigned and modified within the scope of the invention.

For example, while two sets of the lower side supply nozzles 26 forsupplying APM fluid, purified water, and DHF fluid, totaling six (6) arearranged in the manner illustrated in the preferred embodiment, they canbe used in such a way that one lower side injection nozzle 26 may beused for supplying APM fluid and one lower side injection nozzle 26 maybe used for supplying DHF fluid, then two lower side injection nozzles26 may be used for supplying purified water while the remaining twoother lower side injection nozzles 26, 26 may be used for supplying N₂gas for drying the back face of the wafer W, and these nozzles can bealternately selected and used.

Further, while the single wafer type substrate cleaning apparatus can beused as a single apparatus, it can also be used as a basic constructionelement of a wafer cleaning system provided with a loading section, anunloading section or other types of equipment such as placing andmounting robots and the like.

Further still, the chemical fluids employed by the preferred embodimentare mere samples, and hence other chemical fluids such as HPM(HCL+H₂O₂+H₂O), SPM (H₂SO₄+H₂O₂+H₂O), and the like can be used dependingon the object thereof.

What is claimed is:
 1. A single wafer type substrate cleaning apparatusfor cleaning wafers, individually, which are not stored in a cassette,in a sealed cleaning housing, said apparatus comprising: wafer rotarymeans for supporting and rotating each wafer in the cleaning housing inthe horizontal position; a cleaning chamber provided at the outerperipheral portion of the wafer rotary means for forming a cleaningtreatment space for cleaning the wafer which is rotatably supported bythe wafer rotary means; and chemical fluid supply means for supplyingchemical fluids to the front and back faces of the wafer which isrotatably supported by the wafer rotary means, said chemical fluidsupply means being provided in the cleaning housing and comprising upperside supply nozzles for supplying chemical fluids to the front face ofthe wafer from the upper side thereof, and lower side supply nozzles forsupplying chemical fluids to the back face of the wafer from the lowerside thereof; wherein the upper and lower side supply nozzles verticallyand sequentially supply a plurality of chemical fluids to the front andback faces of the wafer which is rotatably supported by the wafer rotarymeans, thereby cleaning the wafer, and purified water is always forcedto flow out of the lower side supply nozzles when chemical fluids arenot supplied therefrom in the series of cleaning treatments.
 2. Thesingle wafer type substrate cleaning apparatus according to claim 1,wherein the upper and lower side supply nozzles are formed of injectionnozzles for injecting and supplying the chemical fluids to the front andback faces of the wafer which is rotably supported by the wafer rotarymeans, and they are disposed by the number corresponding to kinds ofchemical fluids to be supplied.
 3. The single wafer type substratecleaning apparatus according to claim 1 or 2, wherein the lower sidesupply nozzles are directed upward and located on the upper end portionof the rotatable rotary shaft of the wafer rotary means, and means forselectively communicating the lower side supply nozzles with thechemical fluid supply source or the purified water supply source.
 4. Thesingle wafer type substrate cleaning apparatus according to claim 3,wherein the wafer rotary means is has a rotary shaft composed of ahollow cylindrical body, and a pipe having a plurality of chemical fluidsupply passages which vertically penetrates a hollow section of therotary shaft so as to be firmly disposed therein without contacting therotary shaft, and the lower side supply nozzles are directed upward andlocated on an upper end portion of a pipe to communicate with thechemical fluid supply passages of the pipe or with purified waterpassages communicating therewith, and means for selectivelycommunicating the chemical fluid supply passages with the chemical fluidsupply source or the purified water supply source at the lower endportion of the pipe.
 5. The single wafer type substrate cleaningapparatus according to claim 4, wherein a gap defined between an innerperiphery of the rotary shaft of the wafer rotary means and an outerperiphery of the pipe serves as a supply port of an inert gas.
 6. Thesingle wafer type substrate cleaning apparatus according to claim 1 or2, wherein the cleaning chamber is movable up and down relative to thewafer rotary means, and several stages of annular treatment bathsforming the cleaning treatment space are arranged vertically andconcentrically with respect to the inner peripheral portion of thecleaning chamber so as to surround the wafer supported by the waferrotary means, and wherein depending on the cleaning treatment steps, oneof the annular treatment baths is moved to a position corresponding tothe wafer supported by the wafer rotary means when the cleaning chamberis moved up and down.
 7. The single wafer type substrate cleaningapparatus according to claim 6, wherein the cleaning chamber is designedin such a way such that an inner diameter edge of each annular treatmentbath does not contact the outer diameter edge of the wafer supportingsection of the wafer rotary means, and an annular gap is defined betweenthese edges and is designed to be sufficiently narrow to prevent thechemical fluids and purified water from leaking downward.